Throughout this application, various publications are referred to by Arabic numerals in parentheses. These publications are incorporated herein in their entireties and constitute part of the description.
Adjuvant Arthritis (AA) is an experimental model of autoimmune arthritis which can be induced in susceptible strains of rats such as inbred Lewis or Wistar strains upon vaccination with heat-killed Mycobacterium tuberculosis (MT) in complete Freund's Adjuvant (CFA) [1-3]. The disease cannot be induced in resistant strains of rats (e.g., Brown-Norway; Fisher [5, 6], and Lewis rats develop resistance to re-induction of the disease after recovery from arthritis.
The inventors have previously show that resistance to AA can be transferred to a susceptible strain of rats by intravenous infusion of immunoglobulins from the resistant strains, and that resistance is associated with the presence of antibodies against the 65 kD MT heat shock protein (HSP 65) [4].
Heat shock proteins are a family of highly conserved proteins. There is ˜50% amino acid identity between the Mycobacterial HSP 65 and the mammalian HSP 60 [21]. The role of the 65 kD heat shock protein (HSP 65) of MT in the pathogenesis of autoimmune arthritis, both in experimental animals [7, 8] as well as in humans [9-11], has been investigated intensively in the past several years. For example, Barker et al. [32] describe the suppression of arthritogenic immune responses in mice given HSP65 and pristane. The antigen used to elicit the response was full-length HSP65, and no attempt was made to investigate the effect of specific sub-domains or peptides deriving from this protein.
AA can be passively transferred by a T-cell clone reactive to residues 180-188 of the MT HSP 65, and in patients suffering from rheumatoid arthritis (RA), an association between T-cell responses to HSP 65 and early stages of joint inflammation has been found [7, 12-14]. Paradoxically, pre-immunization with the mycobacterial HSP 65 leads to resistance to induction of the disease by MT, and this protective effect is believed to be mediated by T cells specific for HSP 65 [7, 15-16]. Likewise, although arthritic rats develop vigorous T cell responses to self-HSP and to peptide 180-188 of the MT HSP, neither of these is arthritogenic when injected to arthritis-susceptible rats [15, 17]. These results and other suggest that HSP may contain epitopes that are disease-related and other epitopes that confer resistance [5, 19, 20]. Both the pathogenic immune response as well as the protective effect were attributed to anti-HSP T-cells. The following Examples illustrate the fine epitope specificity of the anti-HSP antibodies of arthritis-susceptible and resistant rats.
In addition, the inventors have found that naive Lewis rats lack antibodies to certain epitopes of the mycobacterial HSP 65 which are found naturally in young BN and old naive Lewis rats, and that are acquired by young Lewis rats after recovery from the disease. Analysis of the primary and tertiary structure of the whole MT HSP 65 kD molecule indicated that these “protective” epitopes are potential B-cell epitopes with a non-conserved amino acid sequences that are found on the outer surface of the molecule.
Pre-immunization of Lewis rats with one of the “protective” epitopes prior to induction of the disease induced antibodies against the whole molecule as well as resistance to disease induction. This peptide corresponds also to the self-HSP 60 epitope to which antibodies were found in the arthritis-resistant rats, but not in the arthritis-susceptible naive Lewis rats.